Various electronic devices are mounted on a vehicle. In order to perform power supply and signal transmission to various electronic devices, the vehicle is provided with a plurality of wire harnesses in which a plurality of electrical wires is bundled. Also, in the vehicle, an electrical connection box used for mutual connection of wire harnesses is disposed at an appropriate position.
As an example of the electrical connection box, an electrical connection box disclosed in Patent Literature 1 will be described.
As illustrated in FIGS. 3 and 4, the conventional electrical connection box disclosed in Patent Literature 1 includes an upper case 101 and a lower case 102 made of a synthetic resin, and a plurality of wiring boards a, b, c, and d that is stacked and accommodated in the upper case 101 and the lower case 102. Of the plurality of wiring boards a, b, c, and d, the lowermost wiring board d (wiring board of the lower case 102 side) is configured as a double-sided wiring board in which busbars 104 are disposed on both sides (see FIG. 4).
Each of the wiring boards a, b, c, and d is configured to include an insulating substrate 103, and a busbar 104 having a desired pattern on the insulating substrate 103. In the busbar 104, connection terminals 105 for input and output are erected upward or downward. In the insulating substrate 103, terminal insertion holes 106 are drilled such that connection terminals 105 of the adjacent wiring boards a, b, c, and d are inserted.
In a mounting surface on which the busbars 104 of the respective insulating substrates 103 are mounted, a busbar accommodation groove 115 is provided by protruding ribs 114 at both sides of the busbar 104 according to a desired pattern. In the inner surface of the lower case 102, a water crosslinking prevention rib 117 protrudes on both sides of the busbar 104A for a ground circuit along a desired pattern disposed in a rear surface of the lowermost wiring board d (surface of the lower case 102 side). The crosslinking prevention rib 117 is formed according to the shape of the busbar 104A for the ground circuit and is formed to match with the rib 114 formed in the rear surface of the lowermost wiring board d. Also, both ends of the ribs 114 provided on both sides of the busbar 104A for the ground circuit are closed by a sealing portion (not illustrated) provided corresponding to the connection terminal 105 of the busbar 104A for the ground circuit. In the electrical connection box of the related art, the busbar 104A for the ground circuit in the lowermost wiring board d is surrounded in a sealed state by the rib 114 of the bottom surface of the insulating substrate 103, the water crosslinking prevention rib 117 of the inner surface of the lower case 102, and the sealing portion (not illustrated). Thus, the busbar 104A for the ground circuit is isolated from the other busbars 104. Therefore, there has been proposed a structure for isolating the busbar 104A (specific busbar) for the ground circuit and the other busbars 104.